Researchers identify the Australian lungfish as the most extensive genome sequence of any animals, 14 times larger than human genome sequences.
Australian Lungfish
380 million years ago, fish emerged from the oceans and seas and started to colonize the land. The Neoceratodus fosteri, commonly known as the Australian lungfish, is an endangered air-breathing fish and is one of the few living descendants of the first land explorers.
It typically dwells in slow-flowing and still rivers and waterways in Australia. Its body is peculiar, resembling a cross between newt and fish. Discovered in the 19th century, it was first wrongfully classed as an amphibian.
Today, we know that the Australian lungfish belongs to the lobe-finned fish family, an archaic group of marine animals that gave way to land vertebrates, including humans.
Before aquatic vertebrates set off to colonize the land in the late Devonian era, they first developed traits that would help them survive in the open. Strong, articulate limbs, lungs, and a good sense of smell are only a few examples.
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Studying the Largest Genome Sequence
Siegfried Schloissnig, co-author of the study from the Research Institute of Molecular Pathology in Austria and his colleagues found the lungfish's genome is 43 billion base pairs long--14 times longer than human genome sequences.
Setting a new record for the largest animal genome to date, scientists published the research in Nature.
The Australian lungfish's genome is 30% larger than the previous record-holder: the axolotl, a Mexican amphibian sequences in 2018.
Researchers used high-powered computer sequencers to put together the lungfish genome.
The sequencers used multiple genome copies to account for errors, each fragmented into small pieces of DNA. After, the scientists used algorithms to reassemble the pieces into a full-length genome sequence.
The process took an estimated 100,000 hours of processing power, says Shloissnig.
The Australian lungfish are similar to amphibians in terms of the raw number of genes associated with developing lungs, limbs, and sense of smells.
"When you look at it from a genomic perspective, it is genomically halfway between a fish and land-based vertebrates," explain researchers.
Until recently, the evolutionary history of the Australian lungfish was the center of scientific debate. Biologists were unsure whether lungfishes or coelacanths (different groups of lobed fins) were more closely related to replies, amphibians, mammals, or birds.
Because of this study, researchers bring to the table unequivocal evidence that answers one of the sciences' longest-standing inquiries. According to researchers, coelacanths were the first to diverge from the ancestral line, while lungfish branched off from the line leading to four-legged animals, eventually humans, roughly 420 million years ago.
Elly Tanaka, group leader at theInstitute of Molecular Pathology, says, "There is no doubt that the newly sequenced genome will unveil more of the secrets of the bizarre vertebrate in the future."
Researchers are hopeful that the genome sequences will reveal how adaptation on land occurred and how genomes evolved to their length and size.
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